Paper Foxing Stains on a Historic Manuscript from the Early Qajar Era: Abiotic or Biotic Foxing?

The aim of this study was to identify the nature and cause of foxing spots in a historical manuscript. This manuscript was a Holy Quran from the beginning of the Qajar period and the end of the 18th century. Samples were incubated for 14 days and were evaluated for the presence of fungal activity. UV fluorescence photography, micro X-ray fluorescence spectroscopy and Fourier transform infrared spectroscopy were also used to investigate the characteristics and causes of foxing spots. The results showed that there was no fungal activity in the foxing spots of this manuscript. Based on the morphology of the stain in UV fluorescence photography, these foxing stains are of the Bullseye type, usually associated with metal ions. µXRF spectroscopy also showed a high accumulation of iron and copper at the site of these spots. This indicates abiotic foxing in this manuscript. Based on FTIR spectroscopy and peak deconvolution and fitting by Gaussian function, abiotic foxing increases the cellulose oxidation rate. Intensification of cellulose oxidation in foxing stains can be considered as one of the reasons for paper discoloration.

The Effect of High Lignin Content on Oxidative Nanofibrillation of Wood Cell Wall

Wood from field-grown poplars with different genotypes and varying lignin content (17.4 wt % to 30.0 wt %) were subjected to one-pot 2,2,6,6-Tetramethylpiperidin-1-yl)oxyl catalyzed oxidation and high-pressure homogenization in order to investigate nanofibrillation following simultaneous delignification and cellulose oxidation. When comparing low and high lignin wood it was found that the high lignin wood was more easily fibrillated as indicated by a higher nanofibril yield (68% and 45%) and suspension viscosity (27 and 15 mPa·s). The nanofibrils were monodisperse with diameter ranging between 1.2 and 2.0 nm as measured using atomic force microscopy. Slightly less cellulose oxidation (0.44 and 0.68 mmol·g−1) together with a reduced process yield (36% and 44%) was also found which showed that the removal of a larger amount of lignin increased the efficiency of the homogenization step despite slightly reduced oxidation of the nanofibril surfaces. The surface area of oxidized high lignin wood was also higher than low lignin wood (114 m2·g−1 and 76 m2·g−1) which implicates porosity as a factor that can influence cellulose nanofibril isolation from wood in a beneficial manner.

Efficient Homogeneous TEMPO-mediated Oxidation of Cellulose in Lithium Bromide Hydrates

An appropriate cellulose-dissolving solvent is critical for the homogeneous oxidation of cellulose using TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl)-mediated system. Herein, TEMPO/NaClO/NaClO2 system in lithium bromide hydrates (LBHs) was developed for the homogeneous selective-oxidation of cellulose, which was two-stage protocol involving cellulose dissolution and homogeneous oxidation. Specifically, cellulose was firstly dissolved in LiBr⋅3.5H2O and offered the optimal pH (5.6) for the subsequent TEMPO/NaClO/NaClO2 oxidation without precipitation of the cellulose chains. Effect of reaction conditions on cellulose oxidation was investigated. The results showed that high degree of oxidation (DO) and evenly distributed carboxyl could be achieved. The particle size gradually decreased with DO, and oxidized cellulose with high water solubility and amorphous structure could be obtained. Furthermore, FT-IR, 13C NMR and fractionation analysis verified that cellulose was successfully converted and the carboxyl uniformly distributed onto the cellulose chains. This TEMPO-mediated system using LBHs as solvent presented an efficient method on the homogeneous selective oxidation of primary hydroxyl in cellulose.

Water-soluble chlorophyll-binding proteins from Brassica oleracea allow for stable photobiocatalytic oxidation of cellulose by a lytic polysaccharide monooxygenase

Background Lytic polysaccharide monooxygenases (LPMOs) are indispensable redox enzymes used in industry for the saccharification of plant biomass. LPMO-driven cellulose oxidation can be enhanced considerably through photobiocatalysis using chlorophyll derivatives and light. Water soluble chlorophyll binding proteins (WSCPs) make it is possible to stabilize and solubilize chlorophyll in aqueous solution, allowing for in vitro studies on photostability and ROS production. Here we aim to apply WSCP–Chl a as a photosensitizing complex for photobiocatalysis with the LPMO, TtAA9. Results We have in this study demonstrated how WSCP reconstituted with chlorophyll a (WSCP–Chl a) can create a stable photosensitizing complex which produces controlled amounts of H2O2 in the presence of ascorbic acid and light. WSCP–Chl a is highly reactive and allows for tightly controlled formation of H2O2 by regulating light intensity. TtAA9 together with WSCP–Chl a shows increased cellulose oxidation under low light conditions, and the WSCP–Chl a complex remains stable after 24 h of light exposure. Additionally, the WSCP–Chl a complex demonstrates stability over a range of temperatures and pH conditions relevant for enzyme activity in industrial settings. Conclusion With WSCP–Chl a as the photosensitizer, the need to replenish Chl is greatly reduced, enhancing the catalytic lifetime of light-driven LPMOs and increasing the efficiency of cellulose depolymerization. WSCP–Chl a allows for stable photobiocatalysis providing a sustainable solution for biomass processing.

Kinetic insights into the peroxygenase activity of cellulose-active lytic polysaccharide monooxygenases (LPMOs)

Lytic polysaccharide monooxygenases (LPMOs) are widely distributed in Nature, where they catalyze the hydroxylation of glycosidic bonds in polysaccharides. Despite the importance of LPMOs in the global carbon cycle and in industrial biomass conversion, the catalytic properties of these monocopper enzymes remain enigmatic. Strikingly, there is a remarkable lack of kinetic data, likely due to a multitude of experimental challenges related to the insoluble nature of LPMO substrates, like cellulose and chitin, and to the occurrence of multiple side reactions. Here, we employed competition between well characterized reference enzymes and LPMOs for the H2O2 co-substrate to kinetically characterize LPMO-catalyzed cellulose oxidation. LPMOs of both bacterial and fungal origin showed high peroxygenase efficiencies, with kcat/KmH2O2 values in the order of 105–106 M−1 s−1. Besides providing crucial insight into the cellulolytic peroxygenase reaction, these results show that LPMOs belonging to multiple families and active on multiple substrates are true peroxygenases.

Water-soluble chlorophyll-binding proteins from Brassica oleracea allow for stable photobiocatalytic oxidation of cellulose by a lytic polysaccharide monooxygenase.

Background: Lytic polysaccharide monooxygenases (LPMOs) are indispensable redox enzymes used in industry for the saccharification of plant biomass. LPMO-driven cellulose oxidation can be enhanced considerably through photobiocatalysis using chlorophyll derivatives and light. Water soluble chlorophyll binding proteins (WSCPs) make it is possible to stabilize and solubilize chlorophyll in aqueous solution, allowing for in vitro studies on photostability and ROS production. Here we aim apply a WSCP-Chl α as a photosensitizing complex for photobiocatalysis with the LPMO, TtAA9. Results: We have in this study demonstrated how WSCP reconstituted with chlorophyll a (WSCP-Chl α) can create a stable photosensitizing complex which produces controlled amounts of H2O2 in the presence of ascorbic acid and light. WSCP-Chl α is highly reactive and allows for tightly controlled formation of H2O2 by regulating light intensity. TtAA9 together with WSCP-Chl α shows increased cellulose oxidation under low light conditions, and the WSCP-Chl α complex remains stable after 24 hours of light exposure. Additionally, the WSCP-Chl α complex demonstrates stability over a range of temperatures and pH conditions relevant for enzyme activity in industrial settings.Conclusion: With WSCP-Chl α as the photosensitizer, the need to replenish Chl is greatly reduced, enhancing the catalytic lifetime of light-driven LPMOs and increasing the efficiency of cellulose depolymerization. WSCP-Chl α allows for stable photobiocatalysis providing a sustainable solution for biomass processing.

Water-soluble chlorophyll-binding proteins from Brassica oleracea allow for stable photobiocatalytic oxidation of cellulose by a lytic polysaccharide monooxygenase

Background Lytic polysaccharide monooxygenases (LPMOs) are indispensable redox enzymes used in industry for the saccharification of plant biomass. LPMO-driven cellulose oxidation can be enhanced considerably through photobiocatalysis using chlorophyll derivatives and light. Water soluble chlorophyll binding proteins (WSCPs) make it is possible to stabilize and solubilize chlorophyll in aqueous solution, allowing for in vitro studies on photostability and ROS production. Here we aim apply a WSCP-Chl a as a photosensitizing complex for photobiocatalysis with the LPMO, TtAA9. Results We have in this study demonstrated how WSCP reconstituted with chlorophyll a (WSCP-Chl a) can create a stable photosensitizing complex which produces controlled amounts of H2O2 in the presence of ascorbic acid and light. WSCP-Chl a is highly reactive and allows for tightly controlled formation of H2O2 by regulating light intensity. TtAA9 together with WSCP-Chl a shows increased cellulose oxidation under low light conditions, and the WSCP-Chl a complex remains stable after 24 hours of light exposure. Additionally, the WSCP-Chl a complex demonstrates stability over a range of temperatures and pH conditions relevant for enzyme activity in industrial settings. Conclusion With WSCP-Chl a as the photosensitizer, the need to replenish Chl is greatly reduced, enhancing the catalytic lifetime of light-driven LPMOs and increasing the efficiency of cellulose depolymerization. WSCP-Chl a allows for stable photobiocatalysis providing a sustainable solution for biomass processing.